JP2005231364A - Apparatus for using bubble as virtual valve in microinjector to inject liquid - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To eliminate satellite droplets in a liquid injector. <P>SOLUTION: There is provided an apparatus for forming within a microchannel of a microinjector 12 a bubble 30 to function as a valve mechanism between a chamber 14 and a manifold 16. The valve mechanism provides a high resistance to discharge a liquid from the chamber through the manifold while a fluid is being discharged through an orifice 18, and also provides a low resistance to refill the liquid into the chamber after the liquid is discharged and a bubble bursts. This effectively minimizes crosstalk between adjacent chambers, and increases an injection frequency of the microinjector. A formation of a second bubble 32 within the chamber 14 coalesces with a first formed bubble 30 formed between the chamber 14 and the manifold 16 and abruptly terminates the discharge of the fluid. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

Detailed Description of the Invention

This application claims priority from US Provisional Application No. 60 / 073,293, filed Jan. 23, 1998.

US Government Assisted Research or Development Statement Not applicable.

Reference to attached microfiche Not applicable.

Background art TECHNICAL FIELD OF THE INVENTION The present invention relates generally to liquid injectors, and more particularly to an apparatus for ejecting liquid from a microdevice.

2. 2. Description of Background Art Liquid droplet injectors are widely used for printing in ink jet printers. However, liquid droplet injectors are used in many other potential applications such as fuel injection systems, cell sorting, drug delivery systems, direct printing lithography, and microjet propulsion systems, to name a few examples Can do. Common to all of these applications, there is a need for a reliable, low cost liquid droplet injector capable of supplying high quality droplets with high frequency and high spatial resolution.

  Few devices have the ability to eject liquid droplets of individually uniform droplet size. Among such devices, among the known liquid droplet injection systems, injection with thermally energized bubbles has been most successful due to its simplicity and relatively low cost.

  Thermally energized bubble systems (also known as bubble jet systems) are subject to the disadvantages of crosstalk and satellite droplets. Bubble jet systems use a current pulse that heats the electrodes to boil the liquid in the chamber. When the liquid boils, the bubbles are formed and expand in the liquid and function as a pump to eject the liquid column (which forms a droplet) from the chamber through the orifice. When the current pulse is interrupted, the bubbles collapse and the liquid is refilled into the chamber by capillary forces. The capabilities of such a system include jet velocity and direction, droplet size, maximum jet frequency, crosstalk between adjacent chambers, overshoot and liquid meniscus oscillations before refilling the liquid, and secondary droplet groups Measured by the appearance of. During printing, sub-droplets reduce image sharpness and, under precise liquid control, reduce the accuracy of flow estimation. When the bubble jet injectors are arranged in a dense pitch arrangement, crosstalk occurs and small droplets are ejected from adjacent nozzles.

  In most thermal bubble jet systems, a heater is placed at the bottom of the chamber, which wastes considerable energy on the substrate material. Also, bonding is typically used to attach the nozzle plate to its heater plate, but this bonding limits the nozzle spatial resolution due to the required assembly tolerances. In addition, the bonding process may not be compatible with IC processing, which is important when microinjector arrays with control circuits are desired to be integrated in order to reduce wiring and achieve a compact package. is there.

  In order to solve the crosstalk and overshoot problems, it is common practice to increase the liquid impedance between the chamber and the storage chamber by increasing the channel length or adding a chamber neck. It was. However, these implementations delay the refilling of the liquid into the chamber, thus considerably reducing the maximum drain frequency of the device.

  The most difficult problem with existing inkjet systems is the secondary droplet group. This is because the secondary droplet group causes the image to blur. The secondary droplet group following the main droplet hits the paper surface at a position slightly shifted from the main position when the print head or the paper moves relatively. There is no known effective means or method to solve the subdroplet problem easily and practically and economically.

  Therefore, by minimizing crosstalk without slowing down the liquid refill rate, liquid droplets that maintain a high frequency response while eliminating subdroplets and adding no complexity to design and manufacture. A droplet ejection system is required. The present invention satisfies these requirements as well as other requirements and totally overcomes the disadvantages found in the prior art.

DISCLOSURE OF THE INVENTION The present invention creates a bubble in the microinjector chamber that functions as a valve mechanism between the chamber and the manifold, thereby increasing the liquid exiting the chamber from the chamber during fluid discharge through the orifice. The present invention relates to a device that gives resistance and gives low resistance so that liquid is refilled into the chamber after the liquid is discharged and the bubbles collapse.

  In summary, the apparatus of the present invention generally comprises a chamber and manifold in fluid communication therethrough, an orifice in fluid communication with the chamber, at least one means for forming a bubble between the chamber and the manifold, And a microinjector having means for applying pressure to the device.

  When bubbles are formed at the chamber inlet, the flow of liquid from the chamber to the manifold is restricted. Pressurizing means that applies pressure to the chamber after the formation of bubbles increases the pressure in the chamber so that liquid is forced out of the orifice. After liquid is discharged through the orifice, the bubbles collapse and the chamber is quickly refilled with liquid.

  Since the chamber is pressurized while the bubbles block the chamber from the manifold and adjacent chambers, the crosstalk problem is well minimized.

  In a preferred embodiment of the present invention, the means for forming bubbles comprises a first heater disposed proximate to the chamber. The pressurizing means includes a second heater capable of forming second bubbles in the chamber. Those heaters are arranged close to the orifice. The heaters further include electrodes connected in series and have different resistances due to changes in electrode width. Since the first heater has a narrower electrode than the second heater, the first bubble is formed before the second bubble even when a common electrical signal is applied through them. .

  The first and second bubbles approach each other as they expand and eventually coalesce, thus clearly breaking the liquid flow through the orifice, resulting in the removal or significant reduction of secondary droplets.

  An object of the present invention is to provide a microinjector device that removes subordinate droplet groups.

  Another object of the present invention is to provide a microinjector device that minimizes crosstalk.

  Yet another object of the present invention is to provide a microinjector device that quickly refills a chamber with a liquid after fluid discharge.

  Yet another object of the present invention is to provide a method for ejecting liquid from a microinjector chamber that minimizes sub-droplets.

  Yet another object of the present invention is to provide a method for ejecting fluid from a microinjector chamber that minimizes crosstalk.

  Yet another object of the present invention is to provide a method for ejecting fluid from a micro-injector chamber that quickly refills the chamber with fluid after fluid ejection.

  Further objects and advantages of the present invention will become apparent in the following description. The detailed description herein is made for the purpose of fully disclosing preferred embodiments of the present invention without limitation thereby. The invention will be more fully understood by reference to the accompanying drawings, which are for illustrative purposes only.

DETAILED DESCRIPTION OF THE EMBODIMENTS Referring to the drawings, an apparatus of the present invention embodied for illustrative purposes is shown generally in FIGS. It will be apparent that these devices may be modified in shape and part detail without departing from the basic concepts disclosed herein.

  Referring first to FIG. 1, an array 10 of microinjector devices 12 is shown generally. The array 10 includes a plurality of microinjectors 12 arranged adjacent to each other. Each microinjector includes a chamber 14, a manifold 16, an orifice 18, a first heater 20, and a second heater 22. The first heater 20 and the second heater 22 are typical electrodes connected to a continuous common electrode 24.

  In FIG. 2A, the chamber 14 is provided to be filled with a liquid 26. Liquid 26 can include, but is not limited to, ink, gasoline, oil, chemicals, biomedical solutions, water, or the like, depending on the particular application. The meniscus level 28 of the liquid 26 is generally stable at the orifice 18. Manifold 16 is proximate to and in fluid communication with chamber 14. Liquid from a storage chamber (not shown) is supplied to the chamber 14 through the manifold 16. The first heater 20 and the second heater 22 are located on the chamber 14 in proximity to the orifice 18 in order to prevent heat loss to the substrate. The first heater 20 is disposed near the manifold 16, and the second heater is disposed near the chamber 14. As shown in FIG. 2A, the sectional area of the first heater 20 is narrower than the sectional area of the second heater 22.

  Also, referring to FIG. 2B, since the first heater 20 and the second heater 22 are connected in series, a common electrical pulse is applied to both the first heater 20 and the second heater 22 simultaneously. It can be used to activate. The power dissipation of the current pulse of the first heater 20 having a narrow cross-sectional area is greater than that of the second heater 22 having a wider cross-sectional area. Thus, in response to a common electrical pulse, the first heater 20 is heated more quickly than the second heater 22. This eliminates the need for sequentially operating the first heater 20 and the second heater 22, thereby simplifying the design. The first air bubble 30 is formed between the manifold 16 and the chamber 14 by the activation of the first heater. As the first bubble 30 expands in the direction of arrow P, the first bubble 30 begins to restrict the flow of liquid to the manifold 16. Thereby, a substantial valve is formed that isolates the chamber 14 and shields the adjacent chamber from crosstalk. After the formation of the first bubble 30, the second bubble 32 is formed by the second heater. Since the second bubble 32 expands in the direction of arrow P, the chamber 14 is pressurized, and the liquid 26 is ejected through the orifice 18 as the liquid column 36 in the F direction.

  Further, in FIG. 2C, when the first bubble 30 and the second bubble 32 continue to expand, the first bubble 30 and the second bubble 32 approach each other and block the discharge of the liquid through the orifice 18. When the first heater 20 and the second heater 22 begin to merge, the end 34 of the liquid column 36 is rapidly broken, thus preventing the formation of satellite droplets.

  Also, in FIG. 2D, as a result of the end of the electrical pulse, the first bubble 30 begins to collapse in the direction indicated by P. Since there is nothing restricting the liquid between the manifold 16 and the chamber 14, the liquid 26 quickly refills the chamber 14 in the direction indicated by the arrow R as the first bubble 30 collapses almost instantaneously. .

  As is apparent from the drawing, the method of ejecting the liquid 26 from the microinjector device 12 according to the present invention generally includes the following steps (a) to (e).

  (A) The first bubbles 30 are generated in the chamber 14 filled with the liquid of the microinjector device 12.

  (B) The chamber 14 is pressurized in order to eject the liquid 26 from the chamber 14. This pressurization step includes generating a second bubble 32 in the chamber 14.

  (C) The first bubble 30 in the chamber 14 is enlarged to act as a substantial valve for restricting the flow of liquid between the chamber 14 and the manifold 16.

  (D) The second bubble 32 in the chamber 14 is enlarged. Here, the first bubble 30 and the second bubble 32 approach each other, and the discharge of the liquid from the chamber 14 is rapidly terminated.

  (E) The first bubbles 30 are crushed to promote refilling of the liquid in the chamber 14.

  3 and 4, a micromachining technique combining a surface and a mounted component is used to form the microinjector array 10 on the silicon wafer 38 without any wafer bonding process. The manufacturing process begins with the deposition and patterning of phosphosilicate-glass (PSG) as the chamber sacrificial layer 40 and the low stress silicon nitride 42 as the top layer of the chamber in close proximity.

  The silicon wafer 38 is then etched from its back surface 44 with potassium hydroxide (KOH) to form the manifold 16, as shown in FIGS. The sacrificial PSG layer 40 is removed with hydrofluoric acid (HF). As shown in FIGS. 7 and 8, another KOH etch extends the depth of the chamber 14 with precise time control. Special care is required during this step. This is because the convex angle of the chamber 14 is also eroded and rounded.

  9 and 10, the first heater 20 and the second heater 22 are deposited and patterned. The first heater 20 and the second heater 22 are preferably platinum. Metal lines 44 are formed and an oxide layer 46 is placed on the top surface for film protection. The interconnection 48 between the first heater 20 and the common electrode 24 is disposed under the oxide film layer 46. Finally, in FIGS. 11 and 12, the orifice 18 is formed. Assuming a printing capability of 3 (μm) line width, the orifices 18 should be as small as about 2 (μm) and the pitch between the orifices 18 should be as small as about 15 (μm). It is clear that the convex angle 47 of the chamber 14 is clearly defined as a result of the etching.

  From the above, it is clear that the present invention provides a novel microinjector. The microinjector uses bubbles to restrict the flow of liquid in the microchannel, and prevents bubbles from leaking from the chamber to the manifold while discharging liquid through the orifice. It is also clear that secondary droplet groups are eliminated because the second bubble associated with the first bubble is used to rapidly break the liquid column discharged through the orifice. Although the foregoing description includes a number of limiting descriptions, these are not to be construed as limiting the scope of the invention, but merely a few of the presently preferred embodiments of the invention. This is until illustrated. Accordingly, the spirit of the invention is defined by the appended claims and equivalents thereof.

FIG. 1 is a perspective view of a part of a microinjector array apparatus to which the present invention is applied. FIG. 2A is a cross-sectional view of the chamber and manifold of the apparatus shown in FIG. 2B is a cross-sectional view of the chamber and manifold shown in FIG. 2A illustrating the formation of a first bubble for injecting liquid from an orifice and the subsequent formation of a second bubble. FIG. 2C is a cross-sectional view of the chamber and manifold shown in FIG. 2A illustrating the coalescence of first and second bubbles that block liquid ejection from the orifice. FIG. 2D is a cross-sectional view of the chamber and manifold shown in FIG. 2A illustrating the collapse of a first bubble followed by the collapse of a second bubble that refills the chamber with liquid. FIG. 3 is a top view of a silicon wafer used to manufacture a microinjector array device according to the present invention. FIG. 4 is a cross-sectional view of the silicon wafer shown along line 4-4 in FIG. FIG. 5 is a top view of the silicon wafer shown in FIG. 3 etched from the back to form a manifold. FIG. 6 is a cross-sectional view of the silicon wafer taken along line 6-6 of FIG. FIG. 7 is a top view of the silicon wafer shown in FIG. 5 that has been etched to increase the depth of the chamber. FIG. 8 is a cross-sectional view of the silicon wafer shown along line 8-8 in FIG. FIG. 9 is a top view of the silicon wafer shown in FIG. 7 and shows a state in which a heater is provided on the silicon wafer. 10 is a cross-sectional view of the silicon wafer taken along line 10-10 in FIG. 11 is a top view of the silicon wafer shown in FIG. 9 with orifices formed. FIG. 12 is a cross-sectional view of the silicon wafer taken along line 12-12 of FIG.

Claims (67)

A device that uses bubbles as a substantial valve in a microinjector for injecting liquid,
(A) a chamber including an upper layer for containing a liquid therein;
(B) a passivating layer disposed proximate to the upper layer;
(C) an orifice in fluid communication with the chamber, disposed above the chamber, and passing through both the passivation layer and the upper layer;
(D) first bubble generating means for generating a first bubble that acts as a substantial valve in the chamber when the chamber is filled with a liquid, wherein the passivation is substantially in proximity to the orifice; First bubble generating means disposed between a layer and the upper layer;
(E) a second bubble generating means for generating a second bubble in the chamber following the generation of the first bubble when the chamber is filled with the liquid to be jetted therefrom, generally in proximity to the orifice; And a second bubble generating means disposed between the passivating layer and the upper layer. The apparatus according to claim 1, wherein the first bubble generating means includes a first heater. The apparatus according to claim 2, wherein the second bubble generating means includes a second heater. 4. The apparatus according to claim 3, wherein the first heater and the second heater are arranged so that the first bubble and the second bubble expand toward each other to rapidly block liquid ejection from the chamber. 4. The apparatus of claim 3, wherein the first heater and the second heater are adapted to be driven by a common signal. 4. The apparatus according to claim 3, wherein the first heater and the second heater are connected in series. The apparatus of claim 1, wherein the generation of the first bubble restricts the outflow of liquid from the chamber by acting as a substantial valve. A device that uses bubbles as a substantial valve in a micro-injector that ejects liquid,
(A) a chamber including an upper layer disposed on top;
(B) a passivation layer covering the upper layer;
(C) an orifice in fluid communication with the chamber;
(D) first bubble generating means embedded between the upper layer and the passivation layer in the vicinity of the orifice;
(E) a second bubble generating means embedded between the upper layer and the passivating layer in the vicinity of the orifice, wherein the first bubble generating means introduces the first bubble into the chamber. A device adapted to form, the first bubble acting as a valve that restricts liquid outflow from the chamber. 9. The apparatus according to claim 8, wherein the first bubble generating means includes a first heater, and the second bubble generating means includes a second heater. The apparatus of claim 9, wherein the first heater and the second heater are adapted to be driven by a common signal. The apparatus according to claim 10, wherein the first heater and the second heater are connected in series. A device that uses bubbles as a substantial valve in a microinjector for injecting liquid,
A chamber containing an upper layer and containing a liquid therein;
An orifice in fluid communication with the chamber, disposed above the chamber and passing through the upper layer;
A first heater disposed proximate to the orifice and having a first power dissipation and generating a first bubble in the chamber that acts as a substantial valve when the chamber is filled with liquid;
A second bubble disposed within the chamber following the generation of the first bubble when positioned adjacent to the orifice and having a second power dissipation and when the chamber is filled with liquid to be jetted therefrom. And a second heater that produces a device wherein the first power dissipation is substantially higher than the second power dissipation. The apparatus according to claim 12, wherein the first heater and the second heater are connected in series. 14. The apparatus of claim 13, wherein the first heater has a first resistance value, and the second heater has a second resistance value, the first resistance value being substantially greater than the second resistance value. Expensive device. The apparatus of claim 12, wherein the first heater and the second heater are adapted to be driven by a common signal. 13. The apparatus according to claim 12, wherein the first heater and the second heater are arranged such that the first bubble and the second bubble expand toward each other to rapidly block liquid ejection from the chamber. 13. The apparatus of claim 12, further comprising a passivation layer disposed proximate to the upper layer, wherein the orifice passes through both the passivation layer and the upper layer, and the first heater and the second heater. An apparatus in which a heater is disposed between the passivation layer and the top layer. A device that uses bubbles as a substantial valve in a microinjector for injecting liquid,
(A) a chamber for containing a liquid therein;
(B) an orifice in fluid communication with the chamber, the orifice disposed on the chamber;
(C) means for generating a first bubble in the chamber when the chamber is filled with a liquid, the first bubble generating means being disposed on the chamber adjacent to the orifice;
(D) means for generating a second bubble in the chamber following the generation of the first bubble when the chamber is filled with the liquid to inject the liquid from the chamber; And a second bubble generating means disposed on the chamber in proximity to the orifice. The apparatus according to claim 18, wherein the first bubble generating means includes a first heater. 19. The apparatus according to claim 18, wherein the second bubble generating means includes a second heater capable of generating a second bubble. 21. The apparatus of claim 20, wherein the first heater and the second heater are expanded toward each other such that the first bubble and the second bubble rapidly block liquid ejection from the chamber. Device placed in the. 21. The apparatus of claim 20, wherein the first heater and the second heater are adapted to be driven by a common signal. 21. The apparatus of claim 20, wherein the first heater and the second heater are connected in series. The apparatus of claim 18, wherein the generation of the first bubble restricts the flow of liquid in the chamber by acting as a substantial valve. A device that uses bubbles as a substantial valve in a microinjector for injecting liquid,
(A) a chamber;
(B) a manifold in fluid communication with the chamber to supply liquid to the chamber;
(C) an orifice in fluid communication with the chamber;
(D) means for generating a first bubble in the chamber when the chamber is filled with a liquid, the first bubble generating means disposed outside the chamber in the vicinity of the orifice;
(E) A means for generating a second bubble following the formation of the first bubble, the second bubble generating means being disposed outside the chamber in the vicinity of the orifice, Is disposed between the first bubble generating means and the second bubble generating means, and includes a second bubble generating means for ejecting the liquid in the chamber through the orifice for forming a second bubble. . 26. The apparatus according to claim 25, wherein the first bubble generating means includes a first heater. 27. The apparatus according to claim 26, wherein the second bubble generating means includes a second heater capable of generating a second bubble. 28. The apparatus of claim 27, wherein the first heater and the second heater are adapted to be driven by a common signal. 28. The apparatus of claim 27, wherein the first heater and the second heater are connected in series. 28. The apparatus of claim 27, wherein the first and second heaters are disposed in the orifice such that the first bubble and the second bubble are combined to rapidly block liquid ejection from the orifice. Equipment placed close together. 26. The apparatus of claim 25, wherein the generation of the first bubble restricts the flow of liquid from the chamber during application of pressure by acting as a substantial valve between the chamber and the manifold. apparatus. A method for ejecting liquid from a microchannel having an orifice, comprising:
(A) creating a first bubble proximate to the orifice in a microchannel filled with liquid;
(B) generating a second bubble in the microchannel in the vicinity of the orifice so as to eject liquid from the microchannel by applying pressure to the microchannel, the second bubble; A generation step is performed after the first bubble generation step, and a first bubble generation step in which the first bubble and the second bubble are respectively arranged in parallel with the orifice;
(C) enlarging the first bubble in the microchannel to act as a substantial valve for restricting liquid flow into the microchannel;
(D) enlarging the second bubble in the microchannel, the first bubble and the second bubble approaching each other to rapidly block liquid ejection through the orifice Method. 33. The method of claim 32, wherein the first bubbles are crushed to facilitate the flow of fluid into the microchannel. 35. The method of claim 32, wherein the common signal is used to continuously initiate the generation of both the first bubble and the second bubble. 33. The method of claim 32, wherein the first bubble is enlarged faster than the second bubble. A method of injecting liquid from a microinjector having a chamber, a manifold for supplying liquid to the chamber, and an orifice in fluid communication with the chamber,
(A) a first bubble generating stage for generating a first bubble in the chamber when the chamber is filled with a liquid;
(B) generating a second bubble proximate to the orifice for injecting liquid through the orifice, the second bubble generating step being performed after the first bubble generating step;
(C) combining the first bubble and the second bubble to rapidly block liquid ejection through the orifice. 38. The method of claim 36, further comprising collapsing the first bubble to facilitate liquid flow in the chamber. 40. The method of claim 36, wherein a common signal is used to continuously cause the generation of both the first bubble and the second bubble. 40. The method of claim 36, wherein the first bubble is enlarged faster than the second bubble. A device that uses bubbles as a substantial valve in a microinjector for injecting liquid,
(A) a microchannel;
(B) bubble generating means for generating a first bubble in the microchannel when the microchannel is filled with a liquid;
(C) an apparatus comprising: means for applying pressure to the microchannel to eject the liquid from the microchannel when the microchannel is filled with the liquid; 41. The apparatus of claim 40, wherein the bubble generating means includes a first heater. 42. The apparatus of claim 41, wherein the means for applying pressure to the microchannel includes a second heater capable of generating second bubbles. 43. The apparatus according to claim 42, wherein the first heater and the second heater are arranged such that the first bubble and the second bubble expand toward each other to rapidly block liquid ejection from the chamber. 43. The apparatus of claim 42, wherein the first heater and the second heater are adapted to be driven by a common signal. 43. The apparatus of claim 42, wherein the first heater and the second heater are connected in series. The apparatus of claim 1, wherein the generation of the first bubble restricts the outflow of liquid from the chamber by acting as a substantial valve. A device that uses bubbles as a substantial valve in a microinjector for injecting liquid,
(A) a chamber;
(B) a manifold in fluid communication with the chamber to supply liquid to the chamber;
(C) an orifice in fluid communication with the chamber;
(D) bubble generating means for generating a first bubble in the chamber when the chamber is filled with a liquid;
(E) means for applying pressure to the chamber subsequent to the formation of the first bubble, the means for applying pressure to inject the liquid in the chamber through the orifice for pressurizing the chamber; Equipment provided. 48. The apparatus of claim 47, wherein the first bubble generating means includes a first heater. 49. The apparatus of claim 48, wherein the means for applying pressure to the chamber includes a second heater capable of generating second bubbles. 50. The apparatus of claim 49, wherein the first heater and the second heater are adapted to be driven by a common signal. 50. The apparatus of claim 49, wherein the first heater and the second heater are connected in series. 50. The apparatus of claim 49, wherein the first heater and the second heater are proximate to the orifice such that the first bubble and the second bubble merge to suddenly terminate liquid ejection from the orifice. The device to be arranged as. 48. The apparatus of claim 47, wherein the generation of the first bubble limits liquid flow out of the chamber during pressure by acting as a substantial valve between the chamber and the manifold. Device to do. A method of ejecting liquid from a microchannel,
(A) a first bubble generation stage for generating first bubbles in the microchannel filled with liquid;
(B) applying pressure to the microchannel to eject liquid from the microchannel. 55. The method of claim 54, wherein the applying pressure comprises generating bubbles in the microchannel. 56. The method of claim 55, wherein
(A) enlarging the first bubble in the microchannel to act as a substantial valve to restrict liquid flow between the chamber and the manifold;
(B) enlarging the second bubble in the microchannel such that the first bubble and the second bubble approach each other and suddenly terminate the ejection of the liquid from the microchannel. Including methods. 57. The method of claim 56, further comprising crushing the first bubble to facilitate liquid flow in the microchannel. 56. The method according to claim 55, wherein a common signal is used to continuously generate both the first bubble and the second bubble. 56. The method of claim 55, wherein the first heater and the second heater are connected in series. A first heater is used to generate and enlarge the first bubble, and a second heater is used to generate and enlarge the second bubble, and the first heater is 56. The method of claim 55, wherein the second heater enlarges the first bubble faster than the second bubble enlarges. A method of injecting liquid from a microinjector having a chamber, a manifold for supplying liquid to the chamber, and an orifice in fluid communication with the chamber,
(A) a first bubble generating stage for generating a first bubble in the chamber when the chamber is filled with a liquid;
(B) applying pressure to the chamber to inject liquid through the orifice. 62. The method of claim 61, wherein the applying pressure includes generating a second bubble in the chamber. 64. The method of claim 62, wherein
(A) enlarging the first bubble in the chamber to act as a substantial valve to restrict liquid flow between the chamber and the manifold;
(B) further increasing the size of the second bubble in the microchannel so that the first bubble and the second bubble merge with each other to suddenly end the ejection of the liquid from the microchannel. Including methods. 64. The method of claim 63, further comprising smashing the first bubble to facilitate liquid flow in the microchannel. 64. The method of claim 62, wherein a common signal is used to continuously cause the generation of both the first bubble and the second bubble. 64. The method of claim 62, wherein the first heater and the second heater are connected in series. A first heater is used to generate and enlarge the first bubble, and a second heater is used to generate and enlarge the second bubble, and the first heater is 64. The method of claim 62, wherein the second heater enlarges the first bubble faster than the second bubble enlarges.

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